Various types of end fittings have been used for joining nonmetal flexible conduit to a valve body fitting wherein a tubing reinforcing insert is employed. Examples thereof are U.S. Pat. Nos. 3,830,531, 3,834,742, 3,903,335, 3,915,479 and 3,685,860. In each of these patents, means are provided on the tubing insert for holding it in a removable press fit relationship to the fitting tubing receiving bore or throughbore so that the tubing insert is substantially aligned with the preassembled nut sub-assembly normally employed in compression type fittings.
In U.S. Pat. No. 4,032,177, another type of compression-type end fitting for a nonmetal flexible tubing is disclosed. The fitting includes a tubing receiving bore terminating at an internal stop shoulder with a continuing smaller diameter through bore, a nut sub-assembly of the nut and compression sleeve, which has a tubing reinforcing insert loosely retained within the body and the nut subassembly when the latter are preassembled preparatory to receiving the tubing through the nut sub-assembly. The compression sleeve has a nut receiving throughbore. The insert has a circular flange for loosely retaining the insert within the fitting body bore and has a guide end protruding outwardly of the nut sub-assembly when the latter is assembled to the fitting body to provide for an initial engagement with the tubing and for pre-aligning of the tubing, inset and nut sub-assembly throughbore preparatory to pressing the tubing into the fitting and final tightening of the nut sub-assembly onto the fitting through its use of a suitable hand manipulated tool such as a crescent wrench.